Since perfluoroisopropylbenzene have a perfluoroalkyl group, which exhibits mainly physicochemically distinctive features, they are useful as intermediates or raw materials for synthesizing agricultural chemicals, medicines, dye stuffs surface active agents, wetting agents, dispersing agents, rubber materials, releasing agents, water and oil repelling agents, optical materials, gas separation membrane materials, resist materials, antifouling paints, weather-proofing paints, paper-converting agents, textile-treating agents, functional resins having such characteristics as heat resistance and weather resistance, antistatic agents, photographic toners, liquid crystal materials and solvents (refer, for example, to “Advanced Technology of Halogen Chemicals” published by CMC).
Heretofore, not many reports have been made on examples of production of perfluosoisopropylbenzenes.
Previously known methods in the literature for introducing a perfluoroisopropyl group into a benzene ring are, for example:    (a) a method of replacing a halogen in a halogenated benzenes by using 2-iodoheptafluoropropane in the presence of metallic copper, for example, methods described in (1) Tetrahedron, 25, 5921 (1969), (2) German Patent publication No. 2606982, (3) Journal Chem. Soc. Jpn., 1876 (1972), (4) J. Chem. Soc. Perkin Trans. 1, 661 (1980), and (5) Bull. Chem. Soc. Jpn., 65, 2141 (1992). These methods, however, are industrially disadvantageous in that prior introduction of a halogen atom to the appropriate position of benzenes is necessary, excess of copper is required and the reaction temperature is high. Moreover, depending on the kind of substituents of benzenes, the yield is low and good results are not obtained.    (b) a method of reacting hexafluoropropene on fluoronitrobenzenes in the presence of a fluorine anion, for example, the methods described in (1) J. Chem. Soc. C, 2221 (1968), (2) J. Soc. Org. Synth. Chem., Jpn., 27, 993 (1969), (3) J. Chem. Soc. Jpn., 198 (1976) and (4) Tetrahedron, 51, 13167 (1995). In these methods, however, the substrates which can be used are restricted to those which have been strongly activated by electron withdrawing groups, e.g., perfluoronitrobenzenes and dinitrofluorobenzenes, so that the methods are limited as to the substituent, structure, etc. of obtainable compounds.    (c) a method of reacting an unsubstituted or substituted phenyl Grignard reagent with hexafluoroacetone and then reacting 1-hydroxy-1-trifluoromethyl-2,2,2-trifluoroethylbenzenes thus obtained with an appropriate fluorinating agent, for example, the method described in Canadian Pat. No. 1,022,573. This method, however, is not always economically advantageous because it uses in the reaction industrially difficult-to-handle reagents, such as hydrofluoric acid and SF4.    (d) a method of reacting (heptafluoroisopropyl) phenyliodonium trifluoromethanesulfonate with phenols to obtain perfluoroisopropylphenols, described in Bull. Chem. Soc. Jpn., 57, 3361 (1984). This method, however, is not promising for industrial practice owing to the use of expensive reagent and low selectivity as to the perfluoroisopropylated position of the compound obtained.    (e) a method of reacting iodobenzenes, in the presence of palladium catalyst, with a perfluoroisopropylzinc compound prepared from 2-iodoheptafluoropropane and zinc in the system, to obtain perfluoroisopropylbenzenes, described in Chemistry Letters, 137 (1982). This method, however, is not industrially advantageous owing to its reaction conditions wherein zinc is to be used and the reaction needs to be conducted under ultrasonic waves.
In the prior processes for producing perfluoroisopropylbenzenes, the intended compounds are produced by introducing a perfluoroisopropyl group into intended benzenes by the above-mentioned methods or by subjecting the perfluoroisopropylbenzenes produced by the above-mentioned methods to structural transformation. Both processes are not satisfactory in practice.
Since previous processes are thus not suited to practical use, few examples are known of the production of perfluoroisopropylbenzenes. However, since the perfluoroisopropyl group is a substituent having distinctive features both physically and biochemically, the literature in several fields describes the usefulness of benzenes having a perfluoroisopropyl group introduced thereinto.
As to benzoic acids having a perfluoroisopropyl group as a substituent, for example, JP-A-9-319147 discloses that phthalic acids having a perfluoroisopropyl group on the benzene ring is useful as a positively chargeable charge-controlling agent and as a toner for electrostatic image developing, and JP-A-59-69755 discloses that some of the benzoic amides having a perfluoroisopropyl group are useful as a photographic cyan coupler.
As to perfluoroisopropylbenzenesulfonic acids, for exmaple, U.S. Pat. No. 3,501,522 describes that some of the sulfonic acids and their salts are useful as a wetting agent and dispersing agent and discloses a method of producing 4-heptafluorobenzoic acid from 1-methyl-4-(1-trifluoromethyl-1-hydroxy-2,2,2-trifluoroethyl)benzene as the starting material via 1-methyl-4-heptafluoroisopropylbenzene. This method, however, is industrially disadvantageous because it uses highly toxic reagent as SF4 and chromic acid and hence results in high cost of production facilities and waste proposal.
In the previous known methods, in general, it is necessary to introduce a halogen atom beforehand to the position into which a perfluoroisopropyl group is to be introduced, or the benzenes to which a perfluoroisopropyl group can be introduced are limited to those having a certain substituent, such as phenols and nitrobenzenes. Consequently, the kinds of substituents of perfluoroisopropylbenzenes produced in the past are small in number. Furthermore, all of the methods described above are not suited to mass production. Therefore, in spite of the perfluoroisopropyl group being a substituent which has physically distinctive features and is promising for its usefulness in various fields, not much perfluoroisopropylbenzenes have hitherto been produced.